A standard heater for an injection-molding mold has a normally cylindrical casing made of metal and coaxially receiving an electrical resistance-type heater wire normally shaped as a helix. A mass of electrically insulating but thermally conductive potting surrounds the heater wire and fills the interior of the casing. Terminals at one or both ends of the casing connect to the ends of the resistance wire.
Such a heater is seated in a groove in the mold and an electrical current is passed through its heater element to heat it and the mold. When the element burns out, which is inevitable, the old heater is pried out and a new one is fitted to the groove, normally being potted in place with heat-conductive material or grout and/or being clamped down in the groove.
It is fairly common for the groove to be nonstraight. Thus the heater must be bent to the necessary nonstraight shape. Since the casing is normally made of a high-alloy steel, this bending must take place in a shop and be carried out to high tolerances in order to ensure a good fit of the heater in the groove. Obviously this bending/fitting operation is expensive and considerably raises the cost of replacing the heaters in a mold plate. Moreover the refitting operation can be delayed as the appropriately bent heaters are made up.